bordonbert
- Posts : 1784
Join date : 2015-01-28
Age : 72
Location : Southern England
by bordonbert Wed Dec 06, 2017 8:21 am
There is a specific HT fuse in the old GM36 labelled FU1 which was a 20mm T400mAL250V (note that is 'T' for slow blow) and it should be about the same for the GM40. It's 400mA at 250V. It would be stamped into the fuse itself. Being in the HT side of things it's supposed to be non-user serviceable and it is definitely best left alone if you aren't used to working inside high voltage gear, but if you do have the experience and know how to open the amp without damaging the anti-tamper warranty checks it is just a standard fuse holder on the circuit board. There is also a 20mm T800mAL250V labelled FU2 for the LT side too. Don't mix the two up.
It isn't unknown for that fuse to go out on you and it stops the amp dead in its tracks as it robs all of the valves of anode voltage HT. You ABSOLUTELY MUST get exactly the correct type as a replacement.
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